Electromagnetically driven pumps, particularly fuel pumps



sheets-sheet 1 Dec. 20, 1966 G. MAIER ETAL ELECTROMAGNETICALLY DRIVEN PUMPS, PARTICULARLY FUEL PUMPS Filed NOV. 18, 1964 Dec. 20, 1966 G.. MAIER ETAL 3,293,516

ELECTROMAGNETICALLY DRIVEN PUMPS, PARTICULARLY FUEL PUMPS Filed Nov. 18, 1964 2 sheets-sheet 2 United States Patent Otice 3,293,516 Patented Dec. 20, 1966 a calms. (Ci. 31e- 123) The present invention relates to pumps.

In particular, the present invention relates to electromagnetically driven pumps, particularly fuel pumps.

Pumps of this type generally include a piston which forms an armature of an electromagnet so that when the latter is energized the piston will be moved in one direction, and a spring opposes the movement of the piston by the electromagnet and returns the piston to a given starting position when the electromagnet is deenergized. In this way, through energizing and deenergizing of the electromagnet, the piston can be reciprocated between a pair of given end positions to provide the desired operation of the pump.

Thus, in these known pumps movement of the piston in one direction is achieved by the force of the electromagnet, while movement of the piston in the other direction is achieved by the force of the spring. In order to provide some degree of constant pressure during the pressure stroke of the piston, the spring force is in general used to provide the supply or pressure stroke of the piston, while the magnetic force is used for the suction stroke.

Electromagnetically operated pumps of this type, particularly fuel supply pumps, have the disadvantage that the pumps remain stationary and stop operating when the amount of fuel or other liquid supplied by the pump falls below a given minimum value, and then these pumps can no longer be automatically set into operation if the exciting current of the electromagnet is turned on and olf with the aid of a switch which is actuated by the piston. In structures of Ithis latter type it is essential to restart the operation of the pump by the use of an additional starting device provided specically for this purpose.

A primary object of the present invention is to provide an electromagnetic pump of the above type which eliminates the starting and restarting difficulties of the known pumps.

In addition, it is an object of the present invention not only to provide a pump which is self starting at any time, without the aid of any special starting devices, but in addition which will automatically maintain the electromagnet deenergized during substantially one complete stroke of the piston and energized during substantially the entire reverse stroke of the piston.

In particular, it is an object of the present invention to provide a structure which will automatically respond to the position of the piston of the pump for maintaining7 the pump operating properly as well as for starting and stopping the pump whenever required, without the use of any special starting devices.

Yet another object of the present invention is to provide a pump which is composed of quite simple rugged elements, which is relatively inexpensive, which can be incorporated into a unitary compact assembly, and which is very reliable in operation.

With these objects in View the invention includes, in a pump, an electromagnet means capable of being supplied with current through a suitable electrical circuit. A piston means forms an armature of the electromagnet means and is moved along a given stroke from one end position to another end position when the electromagnet means is energized. A spring means opposes the movement of the piston means by the energized electromagnet means and returns the piston means from its other end position back to its one end position when the electromagnet means is deenergized. A switching means of the invention responds to the particular position of the piston means and is operatively connected to the electrical circuit of the electromagnet means for energizing the electromagnet means when the spring means expands to return the piston means to its one end position, this switching means energizing the electromagnet means when the piston means reaches its one end position and maintaining the electromagnet means energized until the piston means reaches its other end position, and the switching means then deenergizes the electromagnet means when the piston means reaches its other end position and maintains the electromagnet means deenergized until the spring means returns the piston means to its one end position.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. l is a longitudinal sectional elevation of one possible embodiment of a pump according to the present invention;

FIG. 2 is a transverse sectional View taken along the line II-II of FIG. 1 in the direction of the arrows;

FIG. 3 is a partly sectional longitudinal elevation taken along the line III-III of FIG. 2 in the direction of the arrows;

FIG. 4 is a wiring diagram of the structure of FIGS. l-3;

FIG. 5 is a longitudinal sectional elevation of another possible embodiment of a pump according to the invention, the section of FIG. 5 being taken along the line V-V of FIG. 6 in the direction of the arrows; and

FIG. 6 is a top plan view of the structure of FIG. 5.

The pump of the invention includes a piston means 1 which forms the armature of an electromagnet means and which is made of a magnetizable material covered with a thin chrome coating. This piston means 1 is capable of reciprocating in a cylindrical bore 3 of an electromagnet means 2 in which the cylindrical bore 3 is surrounded by a magnetic coil and the armature of the electromagnet which is formed by the piston means has a relatively small play in the bore 3 while being free to reciprocate therein. The electromagnet means 2 includes a die-cast or injection molded plastic spool body 4 which carries the magnetic coil S. The hub of the plastic spool body i has a thin-walled section 6 as Well as a relatively short thick-walled section '7 Whose inner diameter is smaller than that of the thin-walled section 6. The interior of the thin-walled section 6 receives a tube 8 made of magnetizable material, and the clearance space in the interior of the tube 3 is of the same diameter as the inner diameter of the thick-walled section 7 of the spool body 4. The tube t5 of magnetic material extends outwardly beyond the body 4 and is xed beyond the body 4 to a ring 9 made of a magnetic material and forming an equivalent of an outwardly directed annular flange of the tube 8. This tube S may have a press t in the ring 9 or may be xed thereto in any other suitable manner. The outer periphery of the ring 9 of magnetic material is pressed into, or otherwise fixed to, a magnetizable iron sleeve 10 which surrounds the spool and which has its end distant from the ring 9 fixed, in the same way as to the ring 9, to a magnetizable ring 1I which extends inwardly along the bottom face of the spool body 4, as viewed in FIG. 1.

3 The bore at the interior of the ring 11 has the same diameter as the inner diameter of the tube 8 and the inner diameter ot the thick-walled section 7 of the spool body 4. The tube S, the thick-walled section 7, and the ring 11 define the inner cylindrical bore 3 of the electromagnet means in which the piston means 1 can reciprocate.

The entire electromagnet means 2, which includes the elements 8 11 which form a path of iiow for the magnetic circuit, is situated in the interior of a plastic housing 12 which is closed at one end, by a cover 13, in a iuid-tight manner. This cover 13 is provided at its central portion with an elongated tube 1d to which an uniliustrated suction conduit of the pump can be connected. The housing 12 is provided at the center of its end wall which is distant from the cover 13 with a tubular portion 15 capable of being connected with an unillustrated pressure conduit through which the pumped liquid is delivered to a desired location such as, in the case of a fuel pump, to the cylinders of an engine. At the entrance of the tube 14 into the cylindrical bore 3 is situated a suction valve 16 which is in the form of a non-return valve permitting the fuel or other liquid to flow from the interior of the tube 1d into the interior of the bore 3 while preventing a fluid How in the reverse direction. The piston means 1 is formed with an axial bore 17 through which the fluid can flow, and in this axial bore of the piston means is situated a pressure valve 1S which is also in the form of a nonreturn valve and which opens and closes in the same way as the valve 16. Thus, during the pressure stroke of the piston the pressure valve 18 will open while the valve 16 will remain closed, and during the suction stroke of the piston the pressure valve 18 will remain closed while the suction valve 16 will open.

A spring means is provided for displacing the piston means 1 along its suction stroke, and this spring means in the illustrated example takes the form of a coil spring 20 situated in the bore 3 and urging the piston means 1 toward the end wall of the housing 12 which is distant from the cover 13. The end of the piston means 1 which is distant from the spring means 2G is provided with a portion 1a of a suitable resilient shock-absorbing material capable of engaging a rubber ring 1b against which the portion 1a of the piston strikes when the piston reaches its position shown in FIG. 1. 1n this latter position of the piston means 1 which is shown in PEG. l, the top end of the piston means 1 is situated at a given distance below the bottom end of the tube The effective air gap of the magnetic circuit which is indicated in dotted lines in FIG. 1 is therefore determined by the distance from the bottom end of the tube S to the top end of the piston means 1. It is to be noted that the tube S has a wall thickness which tapers in a downward direction so that the bottom end of the tube ii has a minimum thickness, and the piston means 1 tapers in the reverse direction so that its top end is of minimum cross section, and as a result of this tapered configuration of the tube 8 and the piston means 1, providing end faces for the tube 8 and the piston means 1 which are as small as possible, the field lines of the magnetic circuit are in the form of concentrated bundles which can pass through the air gap.

A source of direct current is available for energizing the magnetic coil 5, and this source of direct current is capable of being periodically interrupted with the structure described below.

The pump housing 12 is provided with an elongated outwardly bulging portion extending generally parallel to the axis of the pump and formed with a longitudinally extending groove 21 in which is situated an arm 2d made of a non-magnetic material and capable of reciprocating longitudinally in the groove 21. A pair of spoke-like members 22 and 23 are fixed to and project from the portion 1a of the piston means 1 and are directly connected with the arm 24, as by being formed integral therewith, so that the arm 24 rcciprocates with the piston means 1. This arm 2d carries an elongated permanent bar magnet 25 which extends parallel to the axis of the pump. The longitudinally extending outwardly bulging portion of the housing 12 is also formed with a longitudinal bore 26 in which is situated an envelope 27 made ot a non-magnetic material and filled with any suitable protective gas, for example, this envelope 27 being insertable into the bore 25 from the top of the housing 12 betore the cover 13 is applied thereto. The envelope 27 may be in the form of a hermetically sealed glass tube. The ends of the glass tube are molten so as to initimately surround and engage a pair of elongated flexible strips and 29 which form contacts of a switching means of the invention which ot course includes the glass tube as well as the permanent magnet 25, and when the molten glass sets the contacts are hermetically sealed in the interior of the envelope. These elongated contacts 28 and 19 are capable of engaging each other to assume a closed position and of being displaced from each other to assume an open position, and the magnetic contacts Z3 and 29 are under the influence of the magnetic field of the permanent magnet 7,5 when the piston means 1 rind the permanent magnet 25 are in the lower position illustrated in FIGS.' 1 and 3. The switch contacts and 29 automatically open when due to the energizing of the elecrornagnet means 2, the piston means 1 together with the permanent magnet 25 are pulled upwardly through a predetermined distance.

As may be seen from FlG. 4, the switch contact 2S is electrically connected through a resistor E@ with thc base ot a power transistor 31 while the switch contact il; is connected to the negative pole of an unillustrated source of current. The emitter of the transistor 31 is connected to the positive pole of the source of current. A base resistor 32 is connected in parallel with the emitter-base circuit of the transistor. The collector of the transistor is electrically connected with one end of the magnetic coil 5 whose other end is connected to the negative pole of thc source of current. Connected in parallel with the coil 5 is a diode 33 which serves to conduct away the peak voltages induced in the coil when the electromagnet means is deenergized.

The transistor 31, the resistors 3d and 32, as well as the diode 33 are carried by an electrically non-conductive plate 34 supported in the interior of the cover 13 of the pump housing 12. For this purpose the cover 13 has an upwardly directed peripheral portion extending from its transverse wall which closes the housing 12 and surrounding the support plate A. closure plate 35 is .Fixed to the upper face of the peripheral wall of the cover 13, and electrical connector lugs 36 and 37 are carried by the closure plate 35 which together with the cover 13 is fixed to the housing 12 by spring clips 38 and 39 shown in FIG. 3.

When the contacts 28 and 29 assume their closed position engaging each other, the voltage drop across the base resistor 32 places the transistor 31 in its currentconducting condition, so that current fiows throv f. coil 5 and thus the electromagnet means is energized and the piston means 1 is displaced in opposition to the force of the spring 2d in an upward direction, as viewed in FIG. 1. Toward the end of the upward stroke of thc piston, the permanent magnet 25 opens the contacts and 29 so that the transistor 31 is placed in its blocking condition and the coil 5 becomes deenergized. Toward the end of the subsequent return stroke of the piston means 1 derived from the force of the spring 2d the contacts 2S and 29 again close, so that this operating cycle repeats itself.

The piston 1 moves under the infiuence of the spring 211 as well as under the iniuence of the field of the electromagnet Z in a free vibratory manner back and forth inthe bore 3 without engaging the ring 1b at the bottom of the housing 12. The arrangement such that the pull provided by the electromagnet on the piston 1 displaccs the latter through its tull upward stroke while the compressed spring 2t) will then displace the piston through its full downward stroke. During this upward stroke of the piston the valve 1S opens so that Huid flows into the pressure conduit 15, while during the subsequent downward stroke of the piston the latter will displace fluid out of the tube and the valve 16 automatically opens during suction of additional tluid into the bore 3. Thus, during the upward stroke of the piston fuel or other fluid is displaced out of the bore 3 through the piston 1 and the valve 18 into the pump chamber situated beneath the piston 1, this uid being displaced under pressure into this latter chamber.

When and as long as the internal combustion engine does not take any fuel from the conduit 15, through the supply conduit connected thereto, the piston 1 stops reciprocating as a result of the overpressure in the pressure conduit connected to the tube 15, and the piston 1 now remains at its uppermost position at the beginning of its pressure stroke, and in this position no current flows through the coil 5. As long as the pump does not supply any uid it requires no current. However, as soon as fuel or other fluid is taken out of the supply conduit connected to the tube 15, the spring will displace the piston 1 in accordance with the extent to which fuel is consumed, the piston 1 being displaced at this time along its pressure stroke during which the piston 1 moves downwardly, as viewed in FIG. 1, displacing uid out of the tube 15 and into the delivery conduit connected thereto.

The current consumption of the pump therefore automatically adapts itself to the delivery requirements of the pump.

In the embodiment of the invention which is illustrated in FIGS. 5 and 6, the parts which are the same as or correspond in operation to the parts of FIGS. 1 4 are indicated with the same reference characters. In distinction from the structure shown in FIGS. 1-4, the fuel pump of FIGS. 5 and 6 is provided with a die-cast aluminum pump housing 40 formed with a suction tube 41 and having a pressure chamber 42 which is closed at the open end of the housing by a brass closure plate i3 mounted on the housing 10 and fixed to an end surface thereof by a pressure ring 44 which can be pulled toward the housing d@ by unillustrated screws so that the periphery of the closure plate 43 is clamped between the end face of the housing L10 and the ring 44. In contrast to the embodiment of FIGS. 1-4, the envelope 27 as well as the elongated magnet for opening and closing the contacts 28 and 29 extend transversely with respect to the direction of movement of the piston means 1. The envelope 27 is situated within an opening of a carrier plate 45 made of pressboard. This carrier plate 45 is xedly mounted on the pressure ring 44. The carrier plate 15 carries the resistors 3% and 32 which are electrically connected to each other in the manner shown in FIG. 4 and which are required for the operation of the transistor, and the transistor itself as well as the diode 33 for suppressing the inductive peaks upon deenergizing of the coil are also carried by the plate 45, this diode 33 of course being connected in parallel with the coil 5, as shown in FIG. 5.

The permanent magnet 25 of FIGS. 5 and 6 is carried by that end of the shock-absorbing plastic member i6 which is directed toward the envelope 27, this member 46 being pressed into a cutout formed in an end portion of the piston means 1, and the member 46 is formed with a plurality of axially extending through-bores t8 through which the uid can ow out of the cylinder 3 into the pressure chamber 42 when the piston is pulled down wardly into the bore 3 upon energizing of the electromagnet means 2. From the pressure chamber 42 the pumped fuel which is under pressure can ow through an unillustrated delivery conduit capable of being threaded into the threaded opening 4'7 formed in a lateral wall portion of the housing 4NI, a suitable tting being used for this purpose.

When the piston means 1 is at the end of its supply stroke illustrated in FIG. 5, the contacts 28 and 29 engage each other under the influence of the magnetic eld of the permanent magnet 25, so that the transistor 31 provides a flow of current through the coil 5 with the result that the piston 1 moves downwardly in opposition to the spring 2t). The contacts 28, 29 cannot, however, immediately assume their open position because during the downward movement of the piston 1 they are still situated in the eld of the magnet 25. In order, however, to provide a denite moment when the contacts 28 and 29 assume their open position depending upon the position of the piston, the upper end face of the electromagnet carries, at the exposed surface of the ring 9, a pair of magnetizable, short-circuiting angle members 50 and 51 which dene between themselves a space into which the magnet 25 becomes displaced during the downward movement of the piston 1. Through these short-circuiting angle members 5t) and 51 the magnetic Iield of the permanent magnet 25 is directed into the ring 9 and is therefore directed away from the contacts 28 and 29 as soon as the piston 1 has been displaced sutliciently into the bore 3. As a result of the deflection of the magnetic eld of the magnet 25 away from the contacts 2S and 29, these contacts can assume their open position, due to their own inherent resiliency, for example, so that the transistor will interrupt the low of exciting current through the coil 5.

Inasmuch as the contacts 28 and 29 have spread apart from each other in their open position, it is necessary for the permanent magnet 25 to be displaced from its position where the electromagnet means was deenergized toward the envelope 27 during the pressure or delivery stroke of the piston 1, until the eld of the magnet 25 can again close the switch 28, 29. In order to provide an axial limit on the movement of the piston 1 toward the envelope 27, the right short-circuiting magnetic member 51, as viewed in FIG. 5, is provided with a radially extending tongue 52 which extends into a longitudinal groove of the member 4.16 so that when the bottom end of this groove engages the tongue 52 the upward movement of the piston will be terminated, and in this way the automatic starting or restarting of the pump is guaranteed.

It will be understood that each `of the elements described above, or two or more together, may also nd a useful application in other types of pumps differing from the types described above.

While the invention has been illustrated and described as embodied in fuel pumps, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specic aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a pump, in combination, a housing; electromagnet means having a coil and being xedly mounted in said housing; piston means forming an armature of said electromagnet means, said electromagnet means when energized displacing said piston means from one end position to another end position along a given stroke; spring means urging said piston means from said other position in the reverse direction of said given stroke back to said one end position when said electromagnet means is deenergized; an electrical circuit in which said electromagnet means is connected to be supplied with current through said electrical circuit; and switching means connected to said circuit and responding automatically to the position oi said piston means for energizing said electromagnet means when said spring means displaces said piston means to said one end position thereof and for maintaining said electromagnet means energized until said piston means reaches said other end position thereof, said switching means deenergizing said electromagnet means when said piston means reacties said other end position and maintaining said electromagnet means deenergized until said piston means is displaced by said spring means back to said one end position, said switching means including an envelope of non-magnetizabie material lled with a protective gas and being xedly mounted in said housing, and a pair of magnetizable switch contact members situated in said envelope said contact members being constructed so as to tend to stay in an open position and to move to a closed position when subjected to the inuence of a magnetic field, said switching means further including a permanent magnet xed to said piston means for reciprocation therewith, said permanent magnet having a magnetic held which in one end position of said piston means acts on said Contact members of magnetizable material so as to place said contacts in said closed position where they engage each other.

2. In a pump, in combination, a housing; electromagnet means having a coil and being iixediy mounted in said housing; piston means forming an armature of said electromagnet means, said electromagnet means when energized displacing said piston means `from one end position to another end position along a given stroke; spring means urging said piston means from said other position in the reverse direction of said given stroke back to said one end position when said electromagnet means is deenergized; an electrical circuit in which said electromagnet means is connected to be supplied with current through said electrical circuit; and switching means connected to said circuit and responding automatically to the position of said piston means for energizing said electromagnet means when said spring means displaces said piston means to said one end position thereof and for maintaining said electromaget means energized until said piston means reaches said other end position thereof, said switching means deenergizing said electromagnet means When said piston means reaches said other end position and maintaining said electromagnet means deenergized until said piston means is displaced by said spring means back to said one end position, said switching means including an envelope of non-magnetizable material filled with a protective gas and being iixedly mounted in said housing, and a pair of magnetizable switch contact members situated in said envelope said contact members being constructed so as to tend to stay in an open position and to move to a closed position when subjected to the intluence of a magnetic iield, said switching means further including a permanent magnet fixed to said piston means for reciprocation therewith, said permanent magnet having a magnetic rield which in one end position of said piston means acts on said contact members of magnetizable material so as to place said contacts in said closed position where they engage each other, said permanent magnet and said envelope extending transversely with respect to the direction of movement of said piston means.

3. In a pump, in combination, a housing; electromagnet means having a coil and being iixedly mounted in said housing; piston means forming an armature of said electromagnet means, said electromagnet means when energized displacing said piston means from one end position to another end position along a given stroke; spring means urging said piston means from said other position in the reverse direction of said given stroke back to said one end position when said electromagnet means is deenergized; an electrical circuit in which said electromagnet means is connected to be supplied with current through said electrical circuit; and switching means connected to said circuit and responding automatically to the position of said piston means for energizing said electromagnet means when said spring means displaces said piston means to said one end position thereof and for maintaining said electromagnet means energized until said piston means reaches said other end position thereof, said switching means deenergizing said electromagnet means when said piston means reaches said other end position and maintaining said electromagnet means deenergized until said piston means is displaced by said spring means back to said one end position, said switching means including an envelope of non-magnetizable material filled with a protective gas and being fixedly mounted in said housing, and a pair of magnetizable switch contact members situated in said envelope said contact members being constructed so as to tend to stay in an open position and to move to a closed position when subjected to the iniluence of a magnetic iield, said switching means further including a permanent magnet fixed to said piston means for reciprocation therewith, said permanent magnet having a magnetic eld which in one end position et said piston means acts on said contact members of magnetizable material so as to place said contacts in said closed position where they engage each other, said permanent magnet and said envelope extending transversely with respect to the direction of movement of said piston means, said spring means engaging one end of said piston means and said permanent magnet being connected to the opposite end of said piston means and being polarized transversely with respect to the direction of movement of said piston means.

In a pump, in combination, a housing; electromagnet means having a coil and being iixedly mounted in said housing; piston means forming an armature of said electromagnet means, said electromagnet means when energized displacing said piston means from one end position to another end position along a given stroke; spring means urging said piston means from said other position in the reverse direction of said given stroke back to said one end position when said electromagnet means is deenergized; an electrical circuit in which said electromagnet means is connected to be supplied with current through said electrical circuit; and switching means connected to said circuit and responding automatically to the position of said piston means for energizing said electromagnet means when said spring means displaces said piston means to said one end position thereof and for maintaining said electromagnet means energized until said piston means reaches said other end position thereof, said switching means deenergizing said electromagnet means when said piston means reaches said other end position and maintaining said electromagnet means deenergized until said piston means is displaced by said spring means back to said one end position, said switching means including an envelope of non-magnetizable material filled with a protective gas and being ixedly mounted in said housing, and a pair of magnetizable switch contact members situated in said envelope said contact members being constructed so as to tend to stay in an open position and to move to a closed position when subjected to the influence of a magnetic held, said switching means further including a permanent magnet xed to said piston means for reciprocation therewith, said permanent magnet having a magnetic tield which in one end position of said piston means acts on said contact members of magnetizable material so as to place said contacts in said closed poistion where they engage each other, said permanent magnet and said envelope extending transversely with respect to the direction of movement of said piston means, said spring means engaging one end of said piston means and said permanent magnet being connected to the opposite end of said piston means and being polarized transversely with respect to the direction of movement of said piston means, and said switching means including a magnetic shortcircuiting device operatively positioned with respect to said permanent magnet to cooperate with the latter for permitting said contact members to be displaced apart from each other so that said contact members can then assume an open position.

5. In a pump, in combination, a housing; electromagnet means having a coil and being xedly mounted in said housing; piston means forming an armature of said eiectromagnet means, said electromagnet means when energized displacing said piston means from one end position to another end position along a given stroke; spring means urging said piston means from said other position in the reverse direction of said given stroke back to said one end position when said electromagnet means is deenergized; an electrical circuit in which said electromagnet means is connected to be supplied with current through said electrical circuit; and switching means connected to said circuit and responding automatically to the position of said piston means for energizing said electromagnet means when said spring means displaces said piston means to said one end position thereof and for maintaining said electromagnet means energized until said piston means reaches said other end position thereof, said switching means deenergizing said electromagnet means when said piston means reaches said other end position and maintaining said electromagnet means deenergized until said piston means is displaced by said spring means back to said one end position, said switching means including an envelope of nonmagnetizable material filled with a protective gas and being fiXedly mounted in said housing, and a pair of magnetizable switch contact members situated in said envelope said Contact members being constructed so as to tend to stay in an open position and to move to a closed position when subjected to the influence of a magnetic eld, said switching means further including a permanent magnet Xed to said piston means for reciprocation therewith, said permanent magnet having a magnetic field which in one end position of said piston means acts on said Contact members of magnetizable material so as to place said contacts in said closed position where they engage each other, said permanent magnet and said envelope extending transversely with respect to the direction of movement of said piston means, said spring means engaging one end of said piston means and said permanent magnet being connected to the opposite end of said piston means and being polarized transversely with respect to the direction of movement of said piston means, and said switching means including a magnetic short-circuiting device operatively positioned with respect to said permanent magnet to cooperate with the latter forr permitting said contact members to be displaced apart from each other so that said contact members can then assume an open position, said electromagnet means having a cylindrical bore in which said piston means reciprocates and including iron elements, and said short-circuiting device including a pair of short-circuiting angle mem bers connected to said iron elements of said electromagnet means, respectively situated at opposite sides of said bore of said electromagnet means, and respectively defining between themselves a space into which said electromagnet means moves for permitting said contacts to be displaced to their open position.

6. In a pump, in combination, electromagnet means having a coil; piston means forming an armature of said electromagnet means, said electromagnet means when energized displacing said piston means from one end position to another end position along a given stroke; spring means urging said piston means from said other position in the reverse direction of said given stroke back to said one end position when said electromagnet means is deenergized; an electrical circuit in which said electromagnet means is connected to be supplied with current through said electrical circuit; and switching means connected to said circuit and responding automatically to the position of said piston means for energizing said electromagnet means when said spring means displaces said piston means to said one end position thereof and for maintaining said electromagnet means energized until said piston means reaches said other end position thereof said switching means deenergizing said electromagnet means when said piston means reaches said other end position and maintaining said electromagnet means deenergized until said piston means is displaced by said spring means back to said one end position, said switching means including an elongated permanent magnet extending in the direction of movement of said piston means and connected thereto for movement therewith, said switching means further including a magnetic switch constructed so as to tend to stay in an open position and to move to a closed position when subjected to the iniiuence of the magnetic field of said permanent magnet, said magnetic switch means arranged to be subjected to the inuence of the magnetic eld of said permanent magnet when said permanent magnet moves with said piston means to one end position of the latter so that said magnetic switch means will be closed by said permanent magnet in said one end position of said piston means and opened thereby in the other end position of said piston means,

'7. In a pump as recited in claim 6, said switching means further including an envelope of non-magnetizable material housing said magnetic switch.

8. In a pump as recited in claim I, wherein said electrical circuit includes a power transistor, a rst resistor connected in series between the base of said power transistor and one of said switch Contact members, the emitter of said transistor being connected to one end of said coil of said electromagnet means and said other contact member being connected to the other end of said coil, and a second resistor connected in parallel with the emitterbase circuit of said transistor.

References Cited by the Examiner UNITED STATES PATENTS 2,472,067 6/1949 Dickey et al 103-53 2,706,795 4/1955 Dickey 103-53 X 2,768,580 10/1956 Parker 103--53 X 3,151,227 9/1964 Ewart 20D-87 3,214,854 ll/l965 Swan 310--39 X OTHER REFERENCES Websters International Dictionary, 3rd edition, page 1117, G. C. Merriam Co., Springfield, Mass., 1961.

MILTON O. HIRSHFIELD, Prmaly Examiner.

O. L. RADER, Examiner.

C. W. DAWSON, D. F. DUGGAN, Assistant Examiners. 

1. IN A PUMP, IN COMBINATION, A HOUSING; ELECTROMAGNET MEANS HAVING A COIL AND BEING FIXEDLY MOUNTED IN SAID HOUSING; PISTON MEANS FORMING AN ARMATURE OF SAID ELECTROMAGNET MEANS, SAID ELECTROMAGNET MEANS WHEN ENERGIZED DISPLACING SAID PISTON MEANS FROM ONE END POSITION TO ANOTHER END POSITION ALONG A GIVEN STROKE; SPRING MEANS URGING SAID PISTON MEANS FROM SAID OTHER POSITION IN THE REVERSE DIRECTION OF SAID GIVEN STROKE BACK TO SAID ONE END POSITION WHEN SAID ELECTROMAGNET MEANS IS DEENERGIZED; AN ELECTRICAL CIRCUIT IN WHICH SAID ELECTROMAGNET MEANS IS CONNECTED TO BE SUPPLIED WIT CURRENT THROUGH SAID ELECTRICAL CIRCUIT; AND SWITCHING MEANS CONNECTED TO SAID CIRCUIT AND RESPONDING AUTOMATICALLY TO THE POSITION OF SAID PISTON MEANS FOR ENERGIZING SAID ELECTROMAGNET MEANS WHEN SAID SPRING MEANS DISPLACES SAID PISTON MEANS TO SAID ONE END POSITION THEREOF AND FOR MAINTAINING SAID ELECTROMAGNET MEANS ENERGIZED UNTIL SAID PISTON MEANS REACHES SAID OTHER END POSITION THEREOF, SAID SWITCHING MEANS DEENERGIZING SAID ELECTROMAGNET MEANS WHEN SAID PISTON MEANS REACHES SAID OTHER END POSITION AND MAINTAINING SAID ELECTROMAGNET MENS DEENERGIZED UNTIL SAID PISTON MEANS IS DISPLACED BY SAID SPRING BACK TO SAID ONE END POSITION, SAID SWITCHING MEAN INCLUDING AN ENVELOPE OF NON-MAGNETIZABLE MATERIAL FILLED WITH A PROTECTIVE GAS AND BEING FIXEDLY MOUNTED IN SAID HOUDING, AND A PAIR OF MAGNETIZABLE SWITCHING CONTACT MEMBERS SITUATED IN AN ENVELOPE SAID CONTACT MEMBERS BEING CONSTRUCTED TO AS TO TEND TO STAY IN AN OPEN POSITION AND TO MOVE TO A CLOSED POSITION WHEN SUBJECTED TO THE INFLUENCE OF A MAGNETIC FIELD, SAID SWITCHING MEANS FURTHER INCLUDING A PERMANENT MAGNET FIXED TO SAID PISTON MEANS FOR RECIPROCATION THEREWITH, SAID PERMANENT MAGNET HAVING A MAGNETIC FIELD WHICH IS ONE END POSITION OF SAID PISTON MEANS ACTS ON SAID CONTACT MEMBERS OF MAGNETIZABLE MATERIAL SO AS TO PLACE SAID CONTACTS IN SAID CLOSED POSITION WHERE THEY ENGAGE EACH OTHER.
 8. IN A PUMP RECITED IN CHAIN 1, WHEREIN SAID ELECTRICAL CIRCUIT INCLUDES A POWER TRANSISTOR, A FIRST RESISTOR CONNECTED IN SERIES BETWEEN THE BASE OF SAID POWER TRANSISTOR AND ONE OF SAID SWITCH CONTACT MEMBERS, THE EMITTER OF SAID TRANSISTOR BEING CONNECTED TO ONE END OF SAID COIL OF SAID ELECTROMAGNET MEANS AND SAID OTHER CONTACT MEMBER BEING CONNECTED TO THE OTHER END OF SAID COIL, AND A SECOND RESISTOR CONNECTED IN PARALLEL WITH THE EMITTERBASE CIRCUIT OF SAID TRANSISTOR. 